Communications technologies and uses have greatly changed over the last few decades. In the fairly recent past, copper wire technologies were the primary mechanism used for transmitting voice communications over long distances. As computers were introduced the desire to exchange data between remote sites became desirable for many purposes. The introduction of cable television provided additional options for increasing communications and data delivery from businesses to the public. As technology continued to move forward, digital subscriber line (DSL) transmission equipment was introduced which allowed for faster data transmissions over the existing copper phone wire infrastructure. Additionally, two way exchanges of information over the cable infrastructure became available to businesses and the public. These advances have promoted growth in service options available for use, which in turn increases the need to continue to improve the available bandwidth for delivering these services, particularly as the quality of video and overall amount of content available for delivery increases.
One promising technology that has been introduced is the use of optical fibers for telecommunication purposes. Optical fiber network standards, such as synchronous optical networks (SONET) and the synchronous digital hierarchy (SDH) over optical transport networks (OTNs), have been in existence since the 1980s and allow for the possibility to use the high capacity and low attenuation of optical fibers for long haul transport of aggregated network traffic. These standards have been improved upon and today, using OC-768/STM-256 (versions of the SONET and SDH standards respectively), a line rate of 40 gigabits/second is achievable using dense wave division multiplexing (DWDM) on standard optical fibers.
In terms of system scalability, it is desirable to allow a system to freely scale from a minimal to a very large configuration, requiring, as much as possible, the minimum hardware and software for the intended capacity of the system. Basically, systems should be capable of scaling as operators grow, also called “pay as you grow”, which could possibly be achieved with a system that would scale linearly.
Ideally, it should be possible to build a small system, and scale it by simply adding new components or devices to the system in order to provide more capacity. It should be possible to minimize the need to over-provision a system with hardware capabilities in order to allow a system to scale. For example, it should be possible for a system capable of scaling up to 100 blades, to not require a switch fabric supporting 100 blades if only 10 blades are needed to fulfill the current needs of an operator. New hardware components should rather be added to the switch fabric when needed, in order to scale it on demand.
While optical technology is getting more mature, the cost related to its use is decreasing. Also, as systems are getting more requirements for capacity and sustainability, optical-based solutions become more attractive for system architecture designs. However, networking systems have different needs from the ones of large optical networks. Specific solutions might have to be developed on a system basis, rather than on a more generic network basis. While expensive solutions might be affordable for a network, they might not be acceptable at a node level.
As optical-based networks are being deployed, there is an increasing need in providing efficient solutions for switching and routing information within and between such networks. Currently, the specialized optical switches that are available for large optical networks are typically extremely expensive as they are developed for specific types of core networks. That also means that such optical switches must provide flexible solutions and value-added features such as accounting, rate-limiting, etc.
For building networking systems using an internal system network based on optical technologies, simple, scalable, reliable and affordable solutions are needed for optical switches and crossbars. Optical crossbars have the capabilities to redirect an optical wavelength, or lambda, between an input port and an output port of the device. They can be built using technologies such as MEMS, micro-ring resonators, Mach-Zehnder interferometers, etc. Optical crossbars can be used in systems in order to dynamically configure the optical links between the system components, e.g. blades, minimizing the latency, and not requiring any specific header information from the optical signals.
In the context where an optical crossbar would be used as a component of an internal network of a system, it should require a very simple and minimal design, a very small foot-print, a high energy efficiency ratio and a low cost. However, this type of device becomes quite complicated when there are requirements to dynamically support configurations allowing multiple wavelengths (WDM) from an input port to be redirected to the same output port, which is required in systems that are intended to scale.
Current solutions for cross-connecting optically different optical links, such as ROADM devices, are typically based on technologies such as MEMS, tunable optical filters and beam-steering switches. As they are designed primarily to interconnect the optical systems of a metropolitan network, their design is typically relatively complex in order to fulfill requirements such as power balancing, statistics, etc. That kind of device is too expensive, offers too many features and is too big for building an internal system network.
Commercially available “basic” crossbars are capable of cross-connecting electrically the components of a system. However, among those devices which are currently on the market, it seems that there are no solutions for efficiently cross-connecting optically the components of a system.
Accordingly, it would be desirable to provide optical switches or crossbars which overcome the aforedescribed drawbacks.